This invention relates generally to air conditioning systems and, more particularly, to an improved method and apparatus for controlling the humidity in a space.
With conventional air conditioning systems, little effort is made to control the humidity in the space being cooled and, as a result, in order to achieve the degree of desired comfort, it is necessary to bring the space down to a lower temperature than would otherwise be required. Such an xe2x80x9cover coolingxe2x80x9d function is relatively expensive and also may be cause for discomfort to one in the space being cooled.
An improvement was made to the conventional air conditioning system by the addition of a subcooler on the downstream side of the evaporator as shown and described in U.S. patent application Ser. No. 08/520,896, filed on Aug. 30, 1995, now U.S. Pat. No. 5,622,057, Here, the latent affect of the evaporator coil is enhanced by the added subcooler coil, and the humidity is substantially reduced.
Another approach that has been taken to control humidity in a space is that of using desiccants to supplement the conventional air conditioning system. Such a system is shown in U.S. Pat. No. 5,551,245, issued on Sep. 3, 1996. Although such a desiccant system can provide even greater humidity control than that of the subcooler approach mentioned above, the fabrication and installation costs thereof would be substantially greater.
Because of the tight construction of buildings erected today, there is now the condition known as the xe2x80x9csick buildingxe2x80x9d syndrome, wherein there is insufficient leakage of outside air into the building such that the same air is recycled over and over and becomes stale and stagnant. To avoid this problem, there is now an ASHRAE standard code establishing prescribed requirements for minimum replenishment of air volumes in public buildings. This is presently being accomplished by the use of economizers, but present systems will not accommodate the use of 100% outside air since the cooling capacity is generally not sufficient to do so.
It is therefore an object of the present invention to provide an improved method and apparatus for the control of humidity in an air conditioned space.
Another object of the present invention is the provision for ensuring that the air in a building does not become stale.
Yet Another object of the present invention is the provision for controlling humidity in an economical and effective manner.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, a heat recovery device is placed upstream of the evaporator coil of an air conditioning system. The heat recovery device has two air streams flowing therethrough, in a sensible heat exchange relationship. The return air from the space being cooled is passed through the heat recovery device to achieve a sensible heat gain prior to its discharge outside. On the other side of the heat recovery device, supply air is brought in from the outside and passed through the heat recovery device to be cooled and thereby brought closer to the dew point prior to its being passed through the evaporator coil. In this way, the latent effect of the evaporator coil is substantially enhanced and the humidity of the air passing to the space is reduced because of the increased amount of condensation that occurs at the evaporator coil.
By another aspect of the invention, the heat recovery arrangement described above is used in combination with a subcooler placed downstream of the evaporator coil such tha the refrigerant passing to the evaporator is subcooled. In this way, the latent effect of the evaporator coil is further enhanced and the humidity is further reduced.
By yet another aspect of the invention, an evaporative cooler is placed in the flow of the return air stream, upstream of the heat recovery device. The return air is then first cooled prior to its entry into the heat recovery device, thereby increasing the temperature difference from that of the outside air and increasing the cooling effect to that air prior to its being passed to the evaporator coil.
By still another aspect of the invention, the evaporative cooler is placed below the evaporator coil such that the condensate from the evaporator coil can be used as the water for the evaporative cooler medium.
In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate instructions can be made thereto without departing from the true spirit and scope of the invention.